Rhizotrons and minirhizotrons allow repetitive, nondestructive observation of the soil biota. Bias associated with minirhizotron and rhizotron observations, and methods that will help realize the potential of these observational platforms are reviewed. Root density estimates in minirhizotrons are prone to bias due to soil compaction, and poor contact between tube and soil. Density estimates of microarthropods observed in minirhizotrons, are less biased by longer observation periods, low light levels, and good optical resolution. Microarthropods observed in a rhizotron were underrepresented compared with soil cores if they belonged to groups that move little, are transparent, or small. time-lapse video can be used to sample microarthropod density in rhizotrons. Better visualization of all of the biota can be achieved by using long working length microscope objectives, and stains such as fluorescein diacetate, ethidium bromide and the tetrazolium dye, p-Iodonitrotetrazolium Violet. Repeated observation of the same roots allows the use of demographic methods for calculation of root survivorship, turnover, and productivity. In: L. Brussaard & M. J. Kooistra (eds.), International Workshop on Methods of Research on Soil Structure/Soil Biota Interrelationships